1. Field of the Invention
The present invention relates to a heat exchanger for cooling an electronic device.
2. Description of the Prior Art
The operating speed of computers is constantly being improved to create faster computers. With this improvement, comes increased heat generation and a need to effectively dissipate that heat.
Heat exchangers and heat sink assemblies have been used that apply natural or forced convection cooling methods to dissipate heat from electronic devices that are highly concentrated heat sources such as microprocessors and computer chips. These heat exchangers typically use air to directly remove heat from the electronic devices; however air has a relatively low heat capacity. Thus, liquid-cooled units called LCUs employing a cold plate in conjunction with high heat capacity fluids have been used to remove heat from these types of heat sources. Although LCUs are satisfactory for moderate heat flux, increasing computing speeds have required more effective heat sink assemblies.
Accordingly, thermosiphon cooling units (TCUs) have been used for cooling electronic devices having a high heat flux. A typical TCU absorbs heat generated by the electronic device by vaporizing the working fluid housed on the boiler plate of the unit. The boiling of the working fluid constitutes a phase change from liquid-to-vapor state and as such the working fluid of the TCU is considered to be a two-phase fluid. The vapor generated during boiling of the working fluid is then transferred to a condenser, where it is liquefied by the process of film condensation over the condensing surface of the TCU. The heat is rejected into a stream of air flowing through a tube running through the condenser or flowing over fins extending from the condenser. Alternatively, a second refrigerant can flow through the tube increasing the cooling efficiency. The condensed liquid is returned back to the boiler plate by gravity to continue the boiling-condensing cycle.
An example of a cooling system for electronic devices is disclosed in U.S. Pat. No. 6,085,831 to DiGiacomo et al.
The DiGiacomo patent discloses a TCU including a housing having a lower portion for holding a refrigerant and an upper portion having a top wall wherein heat transfer fins are disposed on the top wall. The upper portion of the housing includes a plurality of condensing chambers extending upwardly and outwardly along a single vertical plane from the lower portion of the housing. A TCU comprising a condenser and a boiling chamber is generally limited by the lack of space available for effective condensing. The boiling intensity of the refrigerant over the electronic device is generally high since the heat source is highly concentrated over the small area of the electronic device.
Although the prior art dissipates heat from electronic devices, as computing speeds increase, there is a continuing need for cooling devices having more efficient or alternative heat transfer capabilities as compared to the conventional electronic cooling assemblies.